Geological reconstructions of the East Asian blocks : from the breakup of Rodinia to the assembly of Pangea

Guochun Zhao 대한지질학회 2019 대한지질학회 학술대회 Vol.2019 No.10

Novel Active Voltage Quality Regulator with Adaptive DC-Link Voltage Control

Guochun Xiao,Zhong Zeng,Kai Liu,Zhiliang Hu,Zhaoan Wang 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.6

In this paper, a novel Active Voltage Quality Regulator (AVQR) topology with a thyristor rectifier and an adaptive dclink voltage control strategy are proposed. The proposed AVQR can efficiently mitigate the long duration variations (e.g.undervoltages/overvoltages), voltage imbalances and voltage harmonics. Compared with conventional AVQRs, it can regulate the load voltage very well with a much lower dc-link voltage. This is accomplished by replacing the diode rectifier with a thyristor rectifier. Moreover, its dc-link voltage can vary with the deviations of the supply voltage through the proposed adaptive dc-link voltage control strategy. All of these contribute to its significantly higher efficiency for online operating, which is very important and attractive for many applications. The proposed topology and control strategy are theoretically analyzed in detail. Simulation results are also provided in the paper. Finally, the feasibility and effectiveness of the proposed method are verified by means of experimental results from a 2kVA prototype. Both of the simulation and experimental results show that the proposed AVQR can achieve a much higher efficiency and similar regulation performance when compared with the conventional ones.

Phase Shift Control for Series Active Voltage Quality Regulators

Guochun Xiao,Guofei Teng,Beihai Chen,Jixu Zhang 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4

A phase shift algorithm based on the closed-loop control of dc-link voltage implemented on a series active voltage quality regulator (A VQR) is proposed in this paper. To avoid pumping-up the dc-link voltage, a general phase shift compensation strategy is applied. The relationships among the operation variables are discussed in detail, which is very important for guiding the design of both the main circuit and the control system. Then on the basis of an investigation of the dc-link voltage pumping-up from viewpoint of the active power flow, a novel phase shift control method based on the closed-loop of the dc-link voltage is proposed. This method can adjust the phase of the output voltage gradually and automatically according to the dc-link voltage variation without introducing a phase jump. The effectiveness of the proposed strategy is verified through simulations of a single-phase SkV A prototype and laboratory experiments on both a single-phase SkV A and a three-phase ISkV A prototype.

An electrochemical sensor based on graphene-chitosan-cyclodextrin modification for the detection of Staphylococcus aureus

Li Guochun,Li Jiaxin,Yang Ziyu 한국탄소학회 2024 Carbon Letters Vol.34 No.1

This study reports the synthesis of a novel graphene/chitosan/β-cyclodextrin composite material (GO/CS/β-CD) via a one-step chemical reduction method, which combines the advantages of graphene, chitosan, and β-cyclodextrin. The morphology and structure of the composite were characterized using various techniques, such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Subsequently, sortase A (SA) was immobilized onto the GO/CS/β-CD for the detection of Staphylococcus aureus. The sensor exhibited a good linear relationship within the concentration range of 30–300 CFU/mL, with a detection limit of 12 CFU/mL. The GO/CS/β-CD composite material showed enhanced properties due to the synergistic effect of graphene, chitosan, and β-cyclodextrin. The immobilization of sortase A onto the composite material improved the sensitivity and selectivity of the sensor for the detection of S. aureus. This study presents a novel graphene/chitosan/β-cyclodextrin composite material with immobilized sortase A, demonstrating enhanced sensitivity and selectivity for the detection of Staphylococcus aureus, which has potential for the development of high-performance sensors in various fields.

Novel Active Voltage Quality Regulator with Adaptive DC-Link Voltage Control

Xiao, Guochun,Zeng, Zhong,Liu, Kai,Hu, Zhiliang,Wang, Zhaoan The Korean Institute of Power Electronics 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.6

In this paper, a novel Active Voltage Quality Regulator (AVQR) topology with a thyristor rectifier and an adaptive dclink voltage control strategy are proposed. The proposed AVQR can efficiently mitigate the long duration variations (e.g. undervoltages/overvoltages), voltage imbalances and voltage harmonics. Compared with conventional AVQRs, it can regulate the load voltage very well with a much lower dc-link voltage. This is accomplished by replacing the diode rectifier with a thyristor rectifier. Moreover, its dc-link voltage can vary with the deviations of the supply voltage through the proposed adaptive dc-link voltage control strategy. All of these contribute to its significantly higher efficiency for online operating, which is very important and attractive for many applications. The proposed topology and control strategy are theoretically analyzed in detail. Simulation results are also provided in the paper. Finally, the feasibility and effectiveness of the proposed method are verified by means of experimental results from a 2kVA prototype. Both of the simulation and experimental results show that the proposed AVQR can achieve a much higher efficiency and similar regulation performance when compared with the conventional ones.

Phase Shift Control for Series Active Voltage Quality Regulators

Xiao, Guochun,Teng, Guofei,Chen, Beihai,Zhang, Jixu The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4

A phase shift algorithm based on the closed-loop control of dc-link voltage implemented on a series active voltage quality regulator (AVQR) is proposed in this paper. To avoid pumping-up the dc-link voltage, a general phase shift compensation strategy is applied. The relationships among the operation variables are discussed in detail, which is very important for guiding the design of both the main circuit and the control system. Then on the basis of an investigation of the dc-link voltage pumping-up from viewpoint of the active power flow, a novel phase shift control method based on the closed-loop of the dc-link voltage is proposed. This method can adjust the phase of the output voltage gradually and automatically according to the dc-link voltage variation without introducing a phase jump. The effectiveness of the proposed strategy is verified through simulations of a single-phase 5kVA prototype and laboratory experiments on both a single-phase 5kVA and a three-phase 15kVA prototype.

A Fast Sorting Strategy Based on a Two-way Merge Sort for Balancing the Capacitor Voltages in Modular Multilevel Converters

Fangzhou Zhao,Guochun Xiao,Min Liu,Daoshu Yang 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.2

The Modular Multilevel Converter (MMC) is particularly attractive for medium and high power applications such as High-Voltage Direct Current (HVDC) systems. In order to reach a high voltage, the number of cascaded submodules (SMs) is generally very large. Thus, in the applications with hundreds or even thousands of SMs such as MMC-HVDCs, the sorting algorithm of the conventional voltage balancing strategy is extremely slow. This complicates the controller design and increases the hardware cost tremendously. This paper presents a Two-Way Merge Sort (TWMS) strategy based on the prediction of the capacitor voltages under ideal conditions. It also proposes an innovative Insertion Sort Correction for the TWMS (ISC-TWMS) to solve issues in practical engineering under non-ideal conditions. The proposed sorting methods are combined with the features of the MMC-HVDC control strategy, which significantly accelerates the sorting process and reduces the implementation efforts. In comparison with the commonly used quicksort algorithm, it saves at least two-thirds of the sorting execution time in one arm with 100 SMs, and saves more with a higher number of SMs. A 501-level MMC-HVDC simulation model in PSCAD/EMTDC has been built to verify the validity of the proposed strategies. The fast speed and high efficiency of the algorithms are demonstrated by experiments with a DSP controller (TMS320F28335).

Control Strategy Based on Equivalent Fundamental and Odd Harmonic Resonators for Single-Phase DVRs

Guofei Teng,Guochun Xiao,Leilei Hu,Yong Lu,Yuba Raj Kafle 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4

In this paper, a digital control strategy based on equivalent fundamental and odd harmonic resonators is proposed for single-phase DVRs. By using a delay block, which can be equivalent to a bank of resonators, it rejects the fundamental and odd harmonic disturbances effectively. The structure of the single closed-loop control system consists of a delay block, a proportional gain and a set of zero phase notch filters. The principle of the controller design is discussed in detail to ensure the stability of the system. Both the supply voltage and the load current feedforwards are used to improve the response speed and the ability to eliminate disturbances. The proposed controller is simple in terms of its structure and implementation. It has good performances in harmonic compensation and dynamic response. Experimental results from a 2kW DVR prototype confirm the validity of the design procedure and the effectiveness of the control strategy.

An LCCL Filter and Its Application to a Half-Bridge APF

Jingyang Fang,Guochun Xiao,Yan Zhang 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

In this paper, a novel high order power filter is proposed, named the LCCL filter. Compared with the traditional LCL filter, the LCCL filter composes a parallel resonant branch loop at the switching frequency by paralleling a small capacitor with the line side inductor. The parallel resonance enables the line side branch loop to exhibit infinite impedance at the switching frequency. Particularly, it can attenuate the switching frequency current ripple components much better than the LCL filter, thus decreases grid current THD. Compared with an LLCL filter, the LCCL filter exhibits better attenuation ability in the high frequency domain when the source impedance is considered. Besides, a capacitorcurrent- based active damping controller is easy to design on the basis of the LCCL filter. A half-bridge APF is taken as an example in this paper to discuss the parameter selection and the controller design method based on the LCCL filter. At last, simulation and experimental results validate the feasibility of the proposed LCCL filter.

Control Strategy Based on Equivalent Fundamental and Odd Harmonic Resonators for Single-Phase DVRs

Teng, Guofei,Xiao, Guochun,Hu, Leilei,Lu, Yong,Kafle, Yuba Raj The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4

In this paper, a digital control strategy based on equivalent fundamental and odd harmonic resonators is proposed for single-phase DVRs. By using a delay block, which can be equivalent to a bank of resonators, it rejects the fundamental and odd harmonic disturbances effectively. The structure of the single closed-loop control system consists of a delay block, a proportional gain and a set of zero phase notch filters. The principle of the controller design is discussed in detail to ensure the stability of the system. Both the supply voltage and the load current feedforwards are used to improve the response speed and the ability to eliminate disturbances. The proposed controller is simple in terms of its structure and implementation. It has good performances in harmonic compensation and dynamic response. Experimental results from a 2kW DVR prototype confirm the validity of the design procedure and the effectiveness of the control strategy.